Low total fatty matter (tfm) cleansing bar

ABSTRACT

The present invention provides a cleansing bar composition comprising 10 to 30 wt % soap, 20 to 45 wt % water soluble organic solvent, 20 to 40 wt % water, 4 to 20 wt % electrolyte other than soap.

FIELD OF THE INVENTION

The present invention relates to low total fatty matter cleansing bars.

BACKGROUND OF THE INVENTION

Conventional cleansing bars based on soap for personal washing usually contain over about 70% by weight total fatty matter, the remainder being water (about 10-20%) and other ingredients such as colour, perfume, preservatives, etc. Structurants and fillers are also present in such compositions in amounts, which replace some of the soap in the bar while retaining the desired hardness of the bar. A few known fillers include starch, kaolin and talc.

Transparent soaps have for many years held an aesthetic appeal to consumers. Such bars can however be costly to produce compared to conventional opaque soap bars, due to special processing techniques required to achieve the transparent effect. Transparent bars moreover have one or more properties inferior to those of opaque bars. In particular transparent bars can have a high rate of wear and is comparatively more sticky and soft. In order to produce a transparent bar of relatively good user properties it has been usual to ensure that its soap content is at least about 40 to 60 wt % of the final bar composition. The remaining ingredients usually comprise one or more components believed to be essential to render the bars transparent.

Hard non-milled soap bars containing moisture of less than 35% are also available. These bars have a TFM of about 30-65%. The reduction in TFM has usually been achieved by the use of insoluble particulate materials and/or soluble silicates. Milled bars generally have a water content about 8-15%, and the hard non-milled bars have a water content of about 20-35%.

It is important to deliver sensory properties such as lather and skin feel, preferably by incorporating benefit agents in the formulation without altering the process, ability and physical properties of the bar.

Currently most of the extruded soap bars contain some amount of soluble oil soap content which helps for lathering, and cleansing and insoluble oil soap content for structuring the soap bar. Normally any soap composition contains 5% to 30% of the weight of total soap is soluble soap and rest is insoluble soap. Essentially any soap bar by weight of total soap is will have at least 60% of insoluble soap used only for structuring the soap bar which does not play any role in cleansing. There are some soap bars with 40 to 50 TFM, where TFM is compensated by skin beneficiary agents, moisturizers etc. Overall an extruded soap bar contains 60-76% of soap which helps in structuring the soap bar. Generally cast melt soap bars available in the market range from with 40-60 TFM.

The increasing demand for vegetable oils, such as palm oil, (one of the main sources of oils and fatty acids used by soap manufacturers), and consequent soaring prices has led to severe constraints on the sustainability of the soaps and detergents Industry, as it is becoming increasingly difficult to provide high TFM soaps at a competitive cost, while still making reasonable profits. As a result, the trend is towards lower TFM soaps, being a cost-effective measure.

WO 03/010273 A1 (Unilever) discloses a soap bar comprising: (iii) from 30 to 60 percent by weight of the soap bar of total fatty matter wherein from 1 to 15 percent by weight is the salt of 12-hydroxystearic acid or a precursor thereof; (iv) from 20 to 50 percent by weight of the soap bar of at least one polyhydric alcohol; and (iii) water.

TW341598 (P&G, 1998) relates to a cast molded personal cleansing soap bar. The invention however only demonstrates higher TFM soaps with the desired hardness.

Therefore there is need is to have a low TFM soap bar with good physical, cleansing and sensorial properties.

There is also a need is to have a low TFM transparent cleansing bar with good physical properties.

There is a need to reduce the total insoluble soap content in the bar while maintaining soluble soap or cleansing soap content hence maintaining the physical, cleansing and sensorial properties.

There is also a need to provide a cleansing bar which is economical and which contributes to sustainability by reducing the amount of natural oil content, such as palm oil which is used in the form of insoluble soap in the bar.

SUMMARY OF THE INVENTION

The present invention provides a low TFM cleansing bar with good physical-properties.

One aspect of the present invention provides a cleansing bar composition comprising 10 to 30 wt % soap, 20 to 45 wt % water soluble organic solvent, 20 to 40 wt % water, and 3 to 20 wt % electrolyte other than soap.

These and other aspects features and advantages will become apparent to those of ordinary skill in the art from a reading of the following detailed description and the appended claims.

DETAILED DESCRIPTION OF THE INVENTION

Various components of the composition are described in greater detail below.

The present invention provides a cleansing bar composition comprising 10 to 30 wt % soap, 20 to 45 wt % water soluble organic solvent, 20 to 40 wt % water, and 3 to 20 wt % electrolyte other than soap.

It was a surprising finding of the present invention that the optimum ratio of soap to water and water soluble organic solvent resulted in a low TFM cleansing bar having good sensorial properties and at the same time having a hardness which is capable of being stamped. It was also a surprising finding that the optimum level of electrolyte resulted in a low TFM cleansing bar which is transparent and at the same time of a hardness which is capable of being stamped.

Total Fatty Matter

The term total fatty matter is used very widely and popularly in the field of soaps and detergents. The term Total Fatty Matter, abbreviated to “TFM”, is used to denote the percentage by weight of fatty acid and triglyceride residues present in the personal wash composition without taking into account the accompanying cations. For a soap having 18 carbon atoms, an accompanying sodium cation will generally amount to about 8 percent by weight. Other cations may be employed as desired, for example zinc, potassium, magnesium, alkyl ammonium and aluminium.

The TFM content of disclosed composition is at most 35 wt %, more preferably between 15 to 35 wt %, and most preferably 20 to 30% based on weight of the composition.

Soaps of Fatty Acids

The term soap means salts of fatty acids. Preferably, the soap is soap of C₈ to C₂₄ fatty acids, more preferably of C₁₀ to C₁₈ fatty acids. It is particularly preferred that the soap includes at least 40 wt % soaps of C₈ to C₁₄ fatty acids, more preferably at least 50 wt % and most preferably at least 70 wt % of the total soap content. It is also preferred that the cleansing bars of the present invention includes at most 60 wt % of the soaps of C₁₆ to C₂₂ fatty acids, preferably at most 50 wt % and most preferably at most 30 wt % of the total soap content. It is preferred that 30% to 60% of the total soap content is insoluble soap and 40 to 70% of the total soap content is soluble soap.

The cation may be an alkali metal, alkaline earth metal or ammonium ion, preferably alkali metals. Preferably, the cation is selected from sodium or potassium. The soap may be saturated or unsaturated. Saturated soaps are preferred over unsaturated soaps for stability. The oil or fatty acids may be of vegetable or animal origin.

The soap may be obtained by saponification of oils, fats or fatty acids. The fats or oils generally used to make soap bars may be selected from tallow, tallow stearins, palm oil, palm stearins, soya bean oil, fish oil, castor oil, rice bran oil, sunflower oil, coconut oil, babassu oil, and palm kernel oil. The fatty acids may be from coconut, rice bran, groundnut, tallow, palm, palm kernel, cotton seed or soyabean.

The fatty acid soaps may also be synthetically prepared (e.g. by the oxidation of petroleum or by the hydrogenation of carbon monoxide by the Fischer-Tropsch process). Resin acids, such as those present in tall oil, may also be used. Naphthenic acids may also be used.

The term water-soluble soap wherever used in this description means soap having solubility greater than 2 g/100 g water at 25° C.

Insoluble and Soluble Soaps

Soap bars consist of mixture of soaps with different chain lengths and chain saturations. They are classified as soluble soaps and insoluble soaps. The soluble soaps usually form a hexagonal liquid crystalline phase with water which dissolves in water during washing and provides lather. The insoluble soaps stay in crystalline formats in the bar and provide mechanical strength. The solid crystals present in the soap bar can include kappa, zeta, eta and delta phases. The amount of soluble and insoluble phase in the soap bar is strongly dependent on the water content and the amount of sheer/working the soap bar has been subjected to at temperatures above or below the Krafft point of the soap molecules. Increasing water content results in an increase in the amount of soluble soap and consequently a reduction in soap hardness. Addition of small quantities of electrolyte and perfume can also influence the liquid and solid ratio. Electrolyte reduces the soap solubility and therefore increasing the solid phase amount while perfume increases the soluble soap amount. (Kirk-Othmer Chemical Technology of Cosmetics, 2012).

Soap Phases

It is generally known that soap (cleansing products) exists as a mixture of solid, liquid crystal & isotropic liquid phases. Characterization of these phases is made using low angle X ray diffraction or NMR. Solid phase is further characterized by size.

For the purpose of present invention, the solid phase includes the solid crystals and the liquid phase includes the liquid and the liquid crystal phase.

Liquid crystal phase is formed due to aggregation of micelles & their arrangement pattern, namely-lamellar, hexagonal, these are characterized by NMR due to differential relaxation times (Hand book of detergents Part-E-Uri Zoeller).

In conventional extruded soap, a mixture of two separate crystal types forms at thermodynamic equilibrium. One crystal type, referred to as delta phase, is composed of the less soluble saturated long-chain soaps (e.g., C16 and C18 soaps) and is dispersed in a continuum of another crystal type composed of the more soluble saturated short-chain soaps and unsaturated soaps (e.g., C12 and C18:1 soaps), referred to as eta phase. The configuration of less soluble soaps dispersed in a continuum of more soluble soaps can be compared to “bricks and mortar” structure. The continuous phase (the “mortar”), which is composed of the more soluble soaps, will also contain more water than the dispersed phase (the “bricks”), which is composed of the less soluble soaps. Further, because solid soap and water have different refractive indices (n=1.5 for solid soap, n=1.0 for water), these two phases will have different refractive indices. Thus, incident light can be scattered as it passes through the different phases in the cleansing bar. Large dispersed soap crystals, entrapped air, and surface roughness will also scatter light, and dark objects present in the cleansing bar will absorb light.

For the purpose of the present invention, “insoluble soap” refer to monovalent salts of saturated fatty monocarboxylic acids having a carbon chain length of 16 to 24, preferably 18 to 22. “Soluble” soap on the other hand refers to monovalent salts of saturated fatty monocarboxylic acids having a carbon chain length of 8 to 14 and monovalent salts of oleic acid and polyunsaturated fatty monocarboxylic acids having a carbon chain length of 8 to 24.

It is particularly preferred that the soap includes at least 40 wt % soaps of C₈ to C₁₄ fatty acids, more preferably at least 50 wt % and most preferably at least 70 wt % of the total soap content. It is also preferred that the cleansing bar of the present invention includes at most 60 wt % of the soaps of C₁₆ to C₂₂ fatty acids, preferably at most 50 wt % and most preferably at most 30 wt %.

Non-Soap Surfactant

In addition to the soap of fatty acids, preferred bars may include a non-soap surfactant, which acts as a co-surfactant and which is selected from anionic, non-ionic, zwitterionic, amphoteric and cationic surfactants. Preferred bars include 0.0001 to 15 wt % co-surfactants based on the weight of the composition. More preferred bars include 2 to 10 wt % co-surfactant and most preferred compositions include 2.5 to 6 wt % co-surfactant based on the weight of the composition.

Suitable anionic surfactants include water soluble salts of organic sulphuric reaction products having in the molecular structure an alkyl radical containing from 8 to 22 carbon atoms, and a radical chosen from sulphonic acid or sulphuric acid ester radicals, and mixtures thereof.

Examples of suitable anionic surfactants are sodium and potassium alcohol sulphates, especially those obtained by sulphating the higher alcohols produced by reducing the glycerides of tallow or coconut oil; sodium and potassium alkyl benzene sulphonates such as those in which the alkyl group contains from 9 to 15 carbon atoms; sodium alkyl glyceryl ether sulphates, especially those ethers of the higher alcohols derived from tallow and coconut oil; sodium coconut oil fatty acid monoglyceride sulphates; sodium and potassium salts of sulphuric acid esters of the reaction product of one mole of a higher fatty alcohol and from 1 to 6 moles of ethylene oxide; sodium and potassium salts of alkyl phenol ethylene oxide ether sulphate with from 1 to 8 units of ethylene oxide molecule and in which the alkyl radicals contain from 4 to 14 carbon atoms; the reaction product of fatty acids esterified with isethionic acid and neutralized with sodium hydroxide where, for example, the fatty acids are derived from coconut oil and mixtures thereof.

The preferred water-soluble synthetic anionic surfactants are the alkali metal (such as sodium and potassium) and alkaline earth metal (such as calcium and magnesium) salts of higher alkyl benzene sulphonates and mixtures with olefin sulphonates and higher alkyl sulphates, and the higher fatty acid monoglyceride sulphates.

Suitable nonionic surfactants can be broadly described as compounds produced by the condensation of alkylene oxide groups, which are hydrophilic in nature, with an organic hydrophobic compound which may be aliphatic or alkyl aromatic in nature.

The length of the hydrophilic or polyoxyalkylene radical which is condensed with any particular hydrophobic group can be readily adjusted to yield a water-soluble compound having the desired degree of balance between hydrophilic and hydrophobic elements.

Particular examples include the condensation product of aliphatic alcohols having from 8 to 22 carbon atoms in either straight or branched chain configuration with ethylene oxide, such as a coconut oil ethylene oxide condensate having from 2 to 15 moles of ethylene oxide per mole of coconut alcohol; condensates of alkylphenols whose alkyl group contains from 6 to 12 carbon atoms with 5 to 25 moles of ethylene oxide per mole of alkylphenol; condensates of the reaction product of ethylenediamine and propylene oxide with ethylene oxide, the condensate containing from 40 to 80 percent of polyoxyethylene radicals by weight and having a molecular weight of from 5,000 to 11,000; tertiary amine oxides of structure R₃NO, where one group R is an alkyl group of 8 to 18 carbon atoms and the others are each methyl, ethyl or hydroxyethyl groups, for instance dimethyldodecylamine oxide; tertiary phosphine oxides of structure R₃PO, where one group R is an alkyl group of from 10 to 18 carbon atoms, and the others are each alkyl or hydroxyalkyl groups of 1 to 3 carbon atoms, for instance dimethyldodecylphosphine oxide; and dialkyl sulphoxides of structure R₂SO where the group R is an alkyl group of from 10 to 18 carbon atoms and the other is methyl or ethyl, for instance methyltetradecyl sulphoxide; fatty acid alkylolamides; alkylene oxide condensates of fatty acid alkylolamides and alkyl mercaptans.

Suitable cationic surfactants that can be incorporated are alkyl substituted quarternary ammonium halide salts e.g. bis (hydrogenated tallow) dimethylammonium chlorides, cetyltrimethyl ammonium bromide, benzalkonium chlorides and dodecylmethylpolyoxyethylene ammonium chloride and amine and imidazoline salts for e.g. primary, secondary and tertiary amine hydrochlorides and imidazoline hydrochlorides.

Suitable amphoteric surfactants are derivatives of aliphatic secondary and tertiary amines containing an alkyl group of 8 to 18 carbon atoms and an aliphatic radical substituted by an anionic water-solubilising group, for instance sodium 3-dodecylamino-propionate, sodium 3-dodecylaminopropane sulphonate and sodium N-2-hydroxydodecyl-N-methyltaurate.

Suitable zwitterionic surfactants are derivatives of aliphatic quaternary ammonium, sulphonium and phosphonium compounds having an aliphatic radical of from 8 to 18 carbon atoms and an aliphatic radical substituted by an anionic water-solubilising group, for instance 3-(N-N-dimethyl-N-hexadecylammonium) propane-1-sulphonate betaine, 3-(dodecylmethyl sulphonium) propane-1-sulphonate betaine and 3-(cetylmethylphosphonium) ethane sulphonate betaine.

Further examples of suitable detergent-active compounds are compounds commonly used as surface-active agents given in the well-known textbooks “Surface Active Agents”, Volume I by Schwartz and Perry and “Surface Active Agents and Detergents”, Volume II by Schwartz, Perry and Berch.

Water Soluble Organic Solvent

The water soluble organic solvent is preferably selected from the group consisting of polyol, hydrotropes and mixtures thereof. The water soluble organic solvent is preferably in the range of 20 to 45 wt %, more preferably in the range of 25% to 40 wt %, and most preferably in the range of 30 to 40 wt % based on the weight of the composition.

Preferred cleansing bar includes 20% to 45 wt % polyols based on the weight of the composition. Preferred polyols include one or more of glycerol, sorbitol, propylene glycol or polyethylene glycol. Usually a mixture is used. More preferred bar includes 25 to 40 wt % polyols and most preferred bars include 30 to 40 wt % of polyols. Polyhydric alcohols (polyols), such as propylene glycol, may serve as diluents to thin out the otherwise thick mixture of caustic soda and fatty acids.

Other polyhydric alcohols such as glycerol perform as a humectant and moisturizer. A mixture of polyols is usually used. When included, polyethylene glycol used in the invention preferably has a molecular weight of from 200 to 1500 Da.

When sorbitol is included, it is preferably present in 5 to 40 percent, more preferably 8 to 25 percent by weight of the composition. When glycerol is included, it is preferably present in 0.5 to 40 percent, more preferably 0.5 to 25 percent by weight of the composition. When polyethylene glycol is included, it is preferably present in 1 to 15 percent more preferably 2 to 10 percent by weight of the composition. When propylene glycol is included, it is preferably present in 0.1 to 15 percent, more preferably 2 to 10 percent by weight of the composition. It is preferred that the composition includes a mixture of sorbitol, polyethylene glycol and propylene glycol. It is most preferred to further include glycerol in addition to the above listed three polyhydric alcohols.

Polyhydric alcohols suitable for use according to the invention include poly (ethylene glycol), propylene glycol, glycerol and sorbitol, i.e., they include dihydric alcohols and polymers with hydroxyl groups. Especially preferred is a mixture of glycerin and sorbitol. The polyhydric alcohol is suitably added a) before saponification or b) before and after saponification.

Hydrotopes include but are not limited to sodium cumene sulphonate, sodium toluene sulphonate, sodium xylene sulphonate & sodium alkyl aryl sulfonate, their derivatives and combinations thereof.

Electrolyte

Optimum electrolyte content is critical for the present invention as the electrolyte content influences a variety of soap parameters. Addition of small quantities of electrolyte influences the liquid and solid phase ratio. Increasing the electrolyte reduces the soap solubility and therefore increasing the solid phase amount, on the other hand lowering electrolyte levels will make the cleansing bar soft.

The electrolyte contents of the present invention is preferred in the range of 3 to 20 wt %, more preferably in the range of 3.5 to 15 wt % and most preferably in range of 4 to 10% by weight of the composition. Preferred electrolytes of the present invention include sodium sulfate, sodium chloride, sodium acetate, sodium citrate, potassium chloride, potassium sulfate, sodium carbonate and other mono or di or tri salts of alkaline earth metals, more preferred electrolytes are sodium chloride, sodium sulfate, sodium citrate, potassium chloride and especially preferred electrolytes are sodium chloride, sodium sulfate, and sodium citrate and combinations thereof. For the avoidance of doubt is clarified that the electrolyte is a non-soap material.

It is highly preferred that the electrolyte contents of the present invention is in the range of 4 to 20%, more preferably 5 to 19% and most preferably 6 to 18% by weight of the composition.

It was a surprising finding of the present invention that the optimum level of electrolytes is critical for desired hardness and transparency. Random alteration in the electrolyte level will not give the desired hardness and transparency to the cleansing bar.

Alcohol

Prior to saponification process, volatile alcohol and water may be added to the mixture to be saponified. Ethanol is an especially preferred volatile alcohol. Saponification may be carried out by using a suitable alkali. Preferred examples include caustic soda and sodium carbonate. Caustic soda is especially preferred. While it is preferable not to use alkanolamines and good transparency can be achieved without using the same, optionally alkanolamines, like triethanolamine, may be added during saponification in the process of the invention.

The cleansing bar also preferably includes 0.05 to 5 wt % alcohol, more preferably from 0.1 to 4 wt % and most preferably from 0.9 to 3 wt % based on the weight of the composition. These include ethanol and isopropyl alcohol. Isopropyl alcohol is more preferred.

Opacifier

An opacifier may be optionally present in the composition. When opacifiers are present, the cleansing bar is generally opaque, i.e. “opacification”. Examples of opacifiers include titanium dioxide, zinc oxide and the like. A particularly preferred opacifier that can be employed when an opaque rather than a transparent soap composition is desired is ethylene glycol mono- or di-stearate, for example in the form of a 20% solution in sodium lauryl ether sulphate. An alternative opacifying agent is zinc stearate.

The product can take the form of a water-clear, i.e. transparent soap, in which case it will not contain an opacifier, or alternatively, it can take the form of an opaque liquid soap containing an opacifier such as that herein defined.

Water

Preferred cleansing bar includes 20 to 40 wt % water; more preferably 20 to 35 wt % and most preferably 22 to 30 wt % water based on the weight of the composition. More or lesser water may adversely affect transparency.

pH

The pH of preferred bars is 8 to 11, more preferably 9 to 11.

The pH of a solution is expressed as the negative logarithm of the hydrogen ion activity which is related to a millivolt potential of the pH indicating electrode. This electrode is calibrated with standard buffer mixtures whose pH values lie on either side (acidic & basic) of that of the solution which is being measured. About 1 gm of the soap bar is weighed in a beaker & made up to 100 grams by adding distilled water. This mixture is then heated to 50° C. for 10 minutes with stirring, the solution is then cooled to 25° C. and pH is measured.

The present invention provides a cleansing bar composition comprising 10 to 30 wt % soap, 20 to 45 wt % water soluble organic solvent, 20 to 40 wt % water, and 3 to 20 wt % electrolyte other than soap.

It is preferred that the liquid phase of the composition makes up least 65% by weight.

It is also preferred that the total fatty matter of the composition is at most 35% by weight of the composition.

It is preferred that out of the total fatty matter, surfactant is up to 15% by weight of the composition.

It is preferred that the water soluble organic solvent is a polyol.

One embodiment of the present invention provides a composition, wherein 40 to 70 wt % of the soap content is soluble soap. It is more preferable that 42 to 68 wt % of the soap content is soluble soap and most preferably, 45 to 65 wt % of the soap content is soluble soap, i.e, 40 to 70 wt % of 10 to 30% soap by weight of the composition.

In a highly preferred aspect of the present invention that the cleansing bar of the present invention is transparent.

In a preferred aspect the present invention provides a composition, wherein at least 50% of the total soap content is soluble soap, more preferably at least 55% and most preferably at least 60%.

It is preferred that 30% to 60% of the total soap content is insoluble soap.

In a preferred aspect of the present invention is provided a composition, wherein ratio of solid phase to liquid phase of the soap composition is in the range of 1:1.85 to 1:10, more preferably from 1:2 to 1:8 and most preferably from 1:2 to 1:6.

In another preferred aspect of the present invention is provided a composition, wherein iodine value of the soap is preferably at most 20, more preferably at most 10 and most preferably at most 10.

It is preferred that free alkali content in the composition is less than 0.5%.

In a preferred aspect of the present invention, soluble to insoluble soap ratio ranges from 1:1.1 to 1:0.7, more preferably from 1:0.95 to 1:0.65 and most preferably from 1:0.85 to 1:0.6.

In another preferred aspect of the present invention, soap to (polyol+water) ratio is preferably in the range of 0.3:1 to 0.65:1 more preferably from 0.3:1 to 0.6:1 and most preferably from 0.2:1 to 0.5:1.

It is preferred that the hardness of the soap bars which is measured as edge pressing value/edge cracking value measured by the method as provided in the examples ranges from 3000 to 9500 grams, more preferably from 4000 to 8000 grams and most preferably from 6000 to 7500 grams.

It is preferred that the percent transmittance of the composition of the present invention as measured by the method provided in the examples ranges from 20 to 40%, more preferably from 25 to 38% and most preferably from 28 to 36%.

A preferred process for preparing the composition of the present invention, the process comprising steps of: preparing a melt of the composition at a temperature in the range of 40 to 90° C.; pouring the melt into a suitable mould, cooling the composition to a temperature in the range of 20 to 30° C.; and demoulding the composition.

A preferred method of cleansing a surface comprising the steps of applying a composition of the present invention and rinsing the surface with a suitable solvent or wiping the surface with a suitable wipe. It is further preferred that the step of rinsing or wiping the surface is carried out within 5 minutes of applying the composition.

It is preferred to use the composition of the present invention for personal hygiene.

Suitably the present invention can be made in the form of toilet blocks, laundry bars and the like

Other Preferred Ingredients

In addition to the ingredients described earlier, preferred cleansing bar may include other ingredients.

A preferred bar may include up to 30 wt % benefit agents. Preferred benefit agents are moisturizers, emollients, sunscreens and anti-ageing compounds. The agents may be added at an appropriate step during the process of making the bars. Some benefit agents may be introduced as macro domains.

Examples of moisturizers and humectants include cetyl alcohol, CARBOPOL® 934, ethoxylated castor oil, paraffin oils, lanolin and its derivatives. Silicone compounds such as silicone surfactants like DC® 3225C (Dow Corning) and/or silicone emollients, silicone oil (DC-200® ex. Dow Corning) may also be included. Sunscreens such as 4-tertiary butyl-4′-methoxy dibenzoylmethane (available under the trade name PARSOL®1789 from Givaudan) or 2-ethyl hexyl methoxy cinnamate (available under the trade name PARSOL® MCX from Givaudan) or other UV-A and UV-B sun-screens may also be added. Lipids such as cholesterol, ceramides, and pseudoceramides, and exfoliant particles such as polyethylene beads, walnut shells, apricot seeds, flower petals and seeds may also be present. Structurants such as maltodextrin or starch may be used to structure the bars. Preferred bars may also include essential oils such as bergamot and citrus or insoluble extracts of avocado, grape, grapeseed, myrrh, cucumber, watercress, calendula, elder flower, geranium, linden blossom, amaranth, seaweed, gingko, ginseng and other plant extracts.

Further optional ingredients include chelating agents such as ethylene diamine tetra acetic acid, preservatives (e.g. GLYDANT®) antioxidants, and natural and synthetic perfumes. Cationic polymers may be included as conditioners. These include POLYQUATERNIUM®, MERQUAT® polymers, and JAGUAR® polymers.

The composition can also optionally include other ingredients conventionally used in soap such as lather boosters, hemectants such as glycerine, moisturisers, colourants and opacifiers.

Other adjunct materials may include germicides and preservatives. These ingredients normally will be in amounts less than 2 wt %, usually less than 0.5 wt %. Other optional ingredients like anti-oxidants, perfumes, polymers, chelating agents, colourants, deodorants, dyes, emollients, moisturizers, enzymes, foam boosters, germicides, anti-microbials, lathering agents, pearlescers, skin conditioners, stabilisers, superfatting agents, sunscreens may be added in suitable amounts in the process of the invention. Preferably, the ingredients are added after the saponification step and before filtering. Sodium metabisulphite, ethylene diamine tetra acetic acid (EDTA), borax and ethylene hydroxy diphosphonic acid (EHDP) are preferably added to the formulation.

It is preferred that the cleansing bar has no or essentially no opacifiers. By opacifiers is meant compounds which limit the quantity of light passing through the solid composition. When opacifiers are present, the solid composition is generally opaque, i.e. “opacification”. Examples of opacifiers include titanium dioxide, zinc oxide and the like.

Process

Processes for production of soaps have been described by F. W. Wells in “Soap and Chemical Specialties”, Vol. XXXI, No. 6 and 7, June and July 1955.

The soap of the present invention is obtained by saponifying fatty acids or oil or their blends. Suitable fatty acids are the C8-C22 fatty acids. Fatty acids particularly suitable for the invention include stearic acid, lauric acid and palmitic acid. These can also be obtained from plant and/or animal sources, for example tallow fatty acids, palm fatty acids.

The invention will be further described by the following illustrative non-limiting examples. All parts therein are by weight % unless otherwise specified.

EXAMPLES

Control and preferred embodiments of melt cast cleansing bars were made by the usual process.

In a batch size of 1 kg, 100 g palm kernel fatty acid, 200 g glycerin, 90 g stearic and palmitic acid and, 20 g castor oil and butylated hydroxyl toluene (0.1 g) were taken in a vessel and heated till the components were in a fluid state. Solution of 37% sodium citrate dehydrate was added in heated oil blend. Followed by the addition of 47% strength caustic soda lye till the mixture was completely neutralized and there was excess alkali amounting to 0.05%. 25 g additional ethanol was then added followed by addition of common salt, EDTA, EHDP, sodium lauryl sulphate, sorbitol (70 percent solution in water), sodium chloride, sorbitol and sodium metabisulphite (SMBS). The mixing was continued until a clear homogeneous mixture was obtained. Total moisture content in formula was 27% of formulation.

The soap mass was then filtered and colour and perfume were added, followed by cooling in a Schicht cooler. The cast bars were then matured under ambient conditions. After this maturation the bars were cut to a suitable size and matured for another 48 hr. The elongated bars were sliced into unit sized billets which were further stamped in stamping dies to give them distinctive rounded shape.

TABLE 1 Composition of the bars Control 1 Control 2 Control 3 Outside the scope of Invention E1 E2 E3 TFM > 35% & Inside the scope of Electro- electro- 22% Ingredients Invention lyte < 3% lyte < 3% electrolyte TFM 20 23 19 20.57 37.23 17.6 Sodium Salt of fatty acid 22 25 20 22.46 40.6 19.4 Soluble Soap 13 15 12 13.26 21.51 12 Insoluble Soap 9 10 8 9.20 19.09 8 % Insoluble Soap 41 40 40 41 47 32 % Soluble Soap 59 60 60 59 53 48 Sodium Lauryl Sulphate 3 3 2.4 3 4 2.3 Sodium Chloride 0.80 0.80 0.7 0.80 1.2 6 Potassium Chloride — — 6 — — 8 Sodium Citrate 6 6 8 2 0 8 Total Electrolyte 6.80 6.80 14.7 2.80 1.2 22 Propylene glycol — — — — 7 — Polyethylene glycol 200 — — — — 5 — Glycerine 22 20 18 23 10 16 Sorbitol 14 14 11.5 16.80 12 11 Total Polyol 36 34 29.5 39.80 34 27 Water 25 23 28 30 18 28 Total Polyol + Water 61 57 57.5 69.80 52 55 Ratio of Soap to 0.37:1 0.44:1 0.34:1 0.32:1 0.78:1 0.32:1 (polyol + water) Other minor ingredients upto upto upto upto upto upto 100 100 100 100 100 100 Transparency 35 34 31 33 35 14 Hardness 6500 7300 6235 4500 7500 7800

The compositions E1, E2 and E3 are the examples of the present invention, whereas Control 1, Control 2 and Control 3 fall outside the scope of the invention for the reasons as provided in the third row of the table.

The data in table 1 of cleansing bar having different solid to liquid (water+polyols) phase ratio compositions read with the hardness, transparency and sensory data in Tables 2 respectively indicates that soap to (Polyol+water) ratio is critical for getting right hardness and sensory properties despite low TFM and particularly low structuring (insoluble soap).

Test Methodology Example 1: Hardness Analysis

Hardness of soaps compositions, especially of bars, is an important quality control measure. The lower the penetration value, the higher the hardness. Hardness of soaps has direct relation with the formulation thereof. Yet another important point about hardness is that it can vary from time to time. Freshly made soap or detergent bars are slightly softer and accordingly their hardness as expressed in terms of penetration values is on the lower side. However as time progresses, the bars generally tend to lose moisture or other volatile components, which makes the bars harder. Therefore the penetration value is seen to drop (reduce) over a period of time. In high liquid phase bar edges of bar are soft hence hardness measurement in this area will give better reflection of hardness of cleansing bar.

Hardness penetration measurements were made using finished cleansing bars using the TA-XT Plus Texture Analyzer supplier by Stable Micro Systems TM. Force measured for depressing/cracking 2 mm edge of a cleansing bar to a depth of 3 mm indicates the hardness of soap. A Force of more than 6000 gms indicates the bar is hard enough to be taken up for even for stamping. TAXT meter (Model—Taxt express enhanced texture analyser—10 kg capacity) machine was used for controlled force application for measuring hardness of cleansing bar.

Example 2: Sensory Analysis Wear Rate Test

The wear rate of the bar was measured by the following procedure.

Four weighed samples of each test bar are placed on soap trays. Two types of soap trays are employed: those that have drainers or raised grids so the water left on the bar after rinsing is drained away; and no drainers so that water can be added to the tray to allow the bars to become “water-logged”. The trays are coded as follows:

With drainers? Wash temperature (° C.) Yes 25 Yes 40 No 25 No 40

10 ml of distilled water (ambient temperature) are poured into the undrained tray (25° and 40° C.).

Each tablet of soap is treated as follows:

-   -   A washing bowl is filled with about 5 litres of water, at the         desired temperature (20° C. or 40° C.).     -   The test tablets (bars of fixed mass and dimensions) are marked         to identify top face (e.g. by making a small hole with a         needle).     -   Wearing waterproof gloves, the tablets are immersed one at a         time in the water, and twisted 15 times (180° each time) in the         hands above water.     -   The tablet is immersed again in the water and twisted for more         15 times (180° each time) in the hands above water.     -   The treated tablet is briefly immersed in the water to remove         lather.     -   The tablet is placed back on its soap tray, ensuring that the         opposite face is uppermost (e.g., the unmarked face).

The above procedure is carried out 6 times per day for 4 consecutive days, at evenly spaced intervals during each day. Alternate face of each bar is placed in the downward position (facing the bottom of the tray) after each washdown. Between washdowns the soap trays should be left on an open bench or draining board, in ambient conditions. After each washdown cycle, the position of each soap tray/tablet is changed to minimize variability in drying conditions.

At the end of each day, each soap tray with drainer is rinsed and dried. Soap trays without drainers are refilled with 10 ml distilled water (ambient temperature). After the last washdown (4^(th) day), all soap trays are rinsed and dried. Each washed bar is placed in its tray and allowed to dry for up to a period of 9 days. On afternoon of the 5th day, the samples are turned so that both sides of the tablet is allowed to dry. On the 8th day, each tablet is weighed.

The rate of wear is defined as the percent weight loss as follows:

${\% \mspace{14mu} {Wear}} = \frac{\left( {{{initial}\mspace{14mu} {weight}} - {{final}\mspace{14mu} {weight}}} \right)*100}{{initial}\mspace{14mu} {weight}}$

Lather Volume Test

The amount of lather generated by a cleansing bar is an important parameter affecting consumer preference. The lather volume test described herein gives a measure of lather generation under standard conditions, thus allowing objective comparison of different soap formulations.

Lather is generated by trained technicians using a standardised method. The lather is collected and its volume measured.

Washing up bowl 1 per operator capacity 10 litres Soap drainer dishes 1 per sample Surgeons' rubber gloves Tall cylindrical glass beaker 400 ml_, 25 ml_graduated (Pyrex nQ1000) Thermometer Glass rod

Tablet Pre-Treatment:

Wearing the surgeon's glove previously washed in plain soap, wash down all test tablets at least 10 minutes before starting the test sequence. This is best done by twisting them about 20 times through 180° under running water. ii. Place about 5 litres of water of known hardness and at a specified temperature in a bowl. Change the water after each bar of soap has been tested. iii. Take up the tablet, dip it in the water and remove it. Twist the tablet 15 times, between the hands, through 180°. Place the tablet on the soap dish. iv. The lather is generated by the soap remaining on the gloves.

Stage 1: Rub one hand over the other hand (two hands on same direction) 10 times in the same way.

Stage 2: Grip the right hand with the left, or vice versa, and force the lather to the tips of the fingers.

This operation is repeated five times. Repeat Stages 1 and 2. Place the lather in the beaker. v. Repeat the whole procedure of lather generation from paragraph iii, twice more, combining all the lather in the beaker. vi. Stir the combined lather gently to release large pockets of air. Read and record the volume.

Data analysis is carried out by two way analysis of variance, followed by Turkey's Test.

Bar Mush—Mush Immersion Test

Mush is a paste or gel of soap and water, formed when soap is left in contact with water as in a soap-dish. Soluble components of the soap move into solution, and water is absorbed into the remaining solid soap causing swelling, and for most soaps, also re-crystallization. The nature of the mush depends on the balance of these solution and absorption actions. The presence of a high level of mush is undesirable not only because it imparts an unpleasant feel and appearance to the soap, but also especially because the mush may separate from the bar and leaves a mess on the washbasin. Residual mush or soap residue is a known consumer negative.

The Mush Immersion Test described herein gives a numerical value for the amount of mush formed on a bar. The test is carried out as follows:

A rectangular billet from the soap tablet is cut to the required dimensions using a plane, knife or cutting jig. The width and depth of the cut billet are accurately measured (+/−0.1 cm). A line is drawn across the billet 5 cm from the bottom of the billet. This line represents the immersion depth.

The billet is attached to a sample holder and suspend in an empty beaker. Demineralised (or distilled) water at 20° C. is added to the beaker until the water level reaches the 5 cm mark on the billet. The beaker is placed in a water bath at 20° C. (+/−0.5° C.) and left for exactly 2 hours.

The soap-holder+billet is removed, the water emptied from the beaker, and the soap-holder+billet is replaced on the beaker for 1 minute so that excess water can drain off. Extraneous water is shaken off, the billet is removed from the soap-holder, and the weight of the billet standing it on its dry end is recorded (W_(M)).

All the mush from all 5 faces of the billet is carefully scraped off, and any remaining traces of mush are removed by wiping gently with a tissue. The weight of the billet within 5 minutes of scraping is recorded (W_(R)).

The quantitative amount of mush is calculated as follows:

${{Mush}\left( {g\text{/}50\mspace{14mu} {cm}^{2}} \right)} = {\frac{W_{M} - W_{r}}{A} \times 50}$

where A is the surface area.

The amount of absorbed water is also calculated as follows:

${{Absorbed}\mspace{14mu} {water}\mspace{14mu} \left( {g\text{/}50\mspace{14mu} {cm}_{2}} \right)} = {\frac{\left( {W_{M} \times W_{O}} \right)}{A} \times 50}$

where W_(O) is the initial weight.

TABLE 2 TFM (BIS method Avg Mush S. Total fatty matter. Lather Rate of (gm/50 No Product Name IS: 13498-1997) (ml) wear % cm²) 1 marketed 40 218 28.18 9.1 transparent cast melt bar 4 E1 20 220 33 10.2 5 E2 23 284 33 9.6

The Table shows that the preferred Examples of the present invention-E1 and E2, despite having low TFM are at par with a transparent marketed cast melt bar made by the same process and having TFM of 40.

Example 3: Transparency Analysis

Transparency is key attribute for soap transparent soap. Right blend of soap and polyols is essential for achieving correct transparency. A spectrophotometer is employed to measure the amount of light that a sample absorbs. The instrument operates by passing a beam of light through a sample and measuring the intensity of light reaching a detector.

Measuring Transparency Method—Spectrophotometry

A spectrophotometer is an instrument that measures the amount of light that can pass through a matrix (specified path length). It is apparent that less light is allowed to pass through hazy or colored matrix than through a clear material. Spectrophotometer is the device that can quantify the amount of light transmitted through a sample.

Inside a spectrophotometer, light is focused (Light source used was Xenon lamp—30 watts) through a lens system to an entrance slit. The light rays are refocused by a second lens onto an exit slit. Between the second lens and the exit slit is a monochromatic grating which separates the white light into its component wavelengths in much the same fashion as a prism. By proper rotation of the monochromatic grating, specific light wavelengths may be passed on through the exit slit to a chamber. Sample is scanned from 400-700 nm & the maxima of transmittance is chosen automatically by the instrument as wavelength for measurement. The bar is cut to thickness of 12 mm with flat surface without inclination, so that soap when placed in the chamber on the aperture fit without gap. Soap is cut to minimum size of 40 mm×40 mm (volume 5.89 cc; thickness 12 mm) and it is ensured that the 25 mm diameter aperture is completely covered.

This chamber is connected directly to a galvanometer which translates the electrical output of the activated photocell into a specific transmittance value. In between the exit slit and the photocell is a chamber where samples may be placed. A clear specimen will yield 100% transmittance, while a turbid sample will deflect a considerable portion of the light rays and will have a lower percent transmittance. The greater the density, the lower the percent transmittance.

Visible spectrophotometer: uses light in the visible range (400-700 nm) of electromagnetic radiation spectrum.

Transmittance is simply the percentage of light impinging on an object that passes through the object and emerges to be detected by the instrument. It is zero for a completely opaque object and 100% when the object is transparent and all the light is transmitted.

-   -   Transmittance, T=I_(t)/I_(o)         -   % Transmittance, % T=100 T

The beam of light consists of a stream of photons, represented by the purple balls in the simulation shown below. When a photon encounters an analyte molecule (the analyte is the molecule being studied), there is a chance the analyte will absorb the photon. This absorption reduces the number of photons in the beam of light, thereby reducing the intensity of the light beam. Values >25% in coloured bars indicated good transparency.

TABLE 3 Product Name Transparency E1 colored 35% E2 colored 34% E3 colored 31% Marketed 1 colored (transparent) 35% Marketed 2 colored (transparent) 33%

The data in Table 3 shows that that the cleansing bars of the present invention, E1 and E2 are transparent and their transparency is comparable to a marketed colored transparent bars.

Example 4: NMR Analysis

The measurements were made Bruker Minispec Wide line NMR spectrometer. The spectrometer has an operating frequency of 5-60 MHz for protons (1H nucleus). A 10 mm sample probe was used and the magnet temperature was 35 deg. C. FID CPMG (Free induction decay Carr-Purcell Meiboom-Gill Relaxation Dispersion) technique was used for determining the relative phase volumes of various phases present in soap, the pulse sequence and the data acquisition. The first 400 data points were recorded from the FID signal following 90° pulse at used (FID CPMG technique) were reported an interval of 0.2 micro seconds. The signal was then refocused using a train of 180° pulses [CPMG] with a value of t=100 (Micro seconds).

TABLE 4 Wide line NMR analysis Total Solid S. Solid Liquid Liquid liquid to No Product Name phase Crystal phase phase Liquid 1 Marketed- 40 10 50 60 1:1.49 40 TFM cast melt bar 2 E2 20 16 63 79 1:4  

Solid phase signifies the insoluble soap or brick which provides rigidity to the cleansing bar. Liquid phase & Liquid crystal phase comprise the mortar phase. In the above table it is seen that even with 50% reduction in brick phase it is possible to achieve a rigid stampable cleansing bar. 

1. A cleansing bar composition comprising: a. 10 to 30 wt % soap, b. 20 to 45 wt % water soluble organic solvent, c. 20 to 40 wt % water, and d. 4 to 20 wt % electrolyte other than soap.
 2. A composition as claimed in claim 1, wherein total fatty matter of the composition is at most 35% by weight of the composition.
 3. A composition as claimed in claim 1, wherein, non-soap surfactant is up to 15% by weight of the composition.
 4. A composition as claimed in claim 1, wherein the water soluble organic solvent is a polyol.
 5. A composition as claimed in claim 1, wherein 40 to 70% of the soap content is soluble soap.
 6. A composition as claimed in claim 1, wherein ratio of solid phase to liquid phase of the bar composition is in the range of 1:1.85 to 1:10.
 7. A composition as claimed in claim 1, wherein iodine value of the soap is at most
 10. 8. A composition as claimed in claim 1, wherein free alkali content in the composition is less than 0.5 wt %.
 9. A composition as claimed in claim 1, wherein the cleansing bar is transparent.
 10. Use of the composition as claimed in claim 1 for personal hygiene.
 11. A process for preparing the composition as claimed in claim 1, the process comprising steps of: a. preparing a melt of the composition at a temperature in the range of 40 to 90° C.; b. pouring the melt into a suitable mould; c. cooling the composition to a temperature in the range of 20 to 30° C.; and d. demoulding the composition.
 12. A method of cleansing a surface comprising the steps of: a. applying a composition as claimed in claim 1 and b. rinsing the surface with a suitable solvent or wiping the surface with a suitable wipe.
 13. A method as claimed in claim 12, wherein the step of rinsing or wiping the surface is carried out within 5 minutes of applying the composition. 